1. Field of the Invention
The invention relates in general to the fabrication of semiconductor integrated circuits (ICs), and more particularly to the metalization process of ICs.
2. Description of the Related Art
In the manufacture of the IC, metal wiring lines are typically used to the electrical connection of devices. Therefore, to form the pattern of the metal wiring lines precisely is one of the crucial qualifications of IC quality. However, the conventional method for metalization tends to cause to problem of incomplete insulation, which directly reduces the yield of the product. Moreover, this problem becomes even more serious for devices of smaller size. To clearly explain the above-mentioned problems, the conventional metalization process is illustrated in FIG. 1A to 1C.
First, referring to FIG. 1A, a semiconductor substrate 10 is provided with a region 11 desired for forming metal wiring lines. The region 11 can be, for example, source/drain regions. This semiconductor substrate 10 is covered with a first dielectric layer 12 but the region 11 is exposed, and on the first dielectric layer 12, parallel oxide pillars 14 are formed. A first metal layer 15 is then formed by sputtering to cover the first dielectric layer 12 and the oxide pillars 14 and to contact the region 11. Next, chemical mechanical polishing (CMP) has been utilized to polish the first metal layer 15 to the same level as the oxide pillars 14.
Referring next to FIG. 1B, a second dielectric layer 16 is formed to cover the first metal layer 15 and the oxide pillars 14. Then, the second dielectric layer 16 is defined to form via holes. After tungsten is deposited into the via hole, etching back and CMP are performed to form a metal wiring line 17.
Referring now to FIG. 1C, a metal layer is sputtered over the second dielectric layer 16 to contact with the metal wiring line 17; after patterned, a second metal layer 18 is formed.
The conventional method includes the process of forming a tungsten plug. Therefore, the steps of tungsten deposition and etching back or CMP are essential for the conventional method. However, theses steps are complicated and costly. Moreover, opening a via hole may result in misalignment and incomplete opening.